Vehicles equipped with power take off (PTO) systems are known which provide a means for mechanical output in addition to the usual drivetrain functions. Such PTO systems commonly provide power for sprayer pumps, chain drives, hydraulic pumps, and generators. Power for the PTO comes from a combustion engine that drives a transmission. The PTO shaft is typically driven directly from the transmission or via a drop box. The operator of the vehicle typically activates the PTO by a switch that engages a clutch. The operator then controls the engine speed by pressing increment/decrement buttons or by working the accelerator pedal. Engine speed must be controlled to provide the changing power needs of the PTO. The operator then must manipulate an input to control whichever accessory that is being powered by the PTO. In the case of a hydraulic system, this may involve moving a lever that controls a hydraulic valve. In this example, the operator must engage the PTO via a switch, change engine speed via switches or the accelerator pedal, and move a lever to control the hydraulic valve at the same time. In many cases, the accessory driven by the PTO is on the rear of the vehicle or in a location that is difficult to see from the operator station. In this case, it is inconvenient for the operator to look behind the operator station and simultaneously work all three controls at the same time.
In addition, it is difficult for the operator to operate the engine and PTO accessory at optimal levels. For instance, the load on the PTO can increase before the operator can increment the engine speed, potentially stalling the engine. Further, it is possible for the operator to increment the engine speed to a speed at which the PTO accessory can be damaged.
U.S. Pat. No. 7,101,312 to Bauerle et al discloses a PTO system with separate controls for engaging the PTO and incrementing/decrementing the engine speed. Bauerle et al does not disclose combining control of multiple PTO functions into a single operator input. Nor does Bauerle et al disclose a transmission controller configured to send an engine control message that contains a maximum allowed PTO accessory speed.